JP4842000B2 - Steering reaction force device - Google Patents

Description

  The present invention relates to a steering reaction force device that controls a steering reaction force according to vehicle behavior.

An electric steering device for reducing a driver's steering force includes a steering reaction force device that generates an auxiliary reaction force in order to improve vehicle deflection suppression performance when a disturbance such as a cross wind acts on the vehicle. Yes (see, for example, Patent Document 1).
A conventional steering reaction device determines, for example, the behavior of a vehicle from a yaw rate, and determines an auxiliary reaction force according to the yaw rate value and the vehicle speed.
Japanese Patent No. 3110891

However, when the auxiliary reaction force is uniformly determined according to the yaw rate (vehicle behavior) and the vehicle speed as in the conventional case, disturbance is applied to the vehicle if the emphasis is on reducing the steering force when turning the vehicle steady. When the vehicle deflection suppression performance is lowered, on the other hand, if the emphasis is placed on improving the vehicle deflection suppression performance when a disturbance is applied to the vehicle, the steering force when the vehicle is turned normally becomes heavy.
That is, in the conventional steering reaction device, it has been difficult to achieve both reduction in steering force and improvement in vehicle deflection suppression performance.
Therefore, the present invention provides a steering reaction force device that can achieve both reduction in steering force and improvement in vehicle deflection suppression performance.

In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a steering reaction force device that controls a steering reaction force according to a vehicle behavior (for example, a yaw rate in an embodiment described later) (for example, an assist in an embodiment described later) In the reaction torque determining means 32), the instability degree detecting means for detecting the instability degree of the vehicle (for example, step S104 in the embodiment described later) and the instability degree of the vehicle detected by the instability degree detecting means. And a correction means for correcting the steering reaction force (for example, step S106 in the embodiment described later). The correction means increases the steering reaction force as the degree of instability of the vehicle increases. The correction amount for the steering reaction force is increased.
With this configuration, even when the vehicle behavior is the same, the steering reaction force can be increased when the degree of instability of the vehicle is large, and the steering reaction force can be decreased when the degree of instability of the vehicle is small. it can.

The invention according to claim 2 is the invention according to claim 1, wherein the degree of instability of the vehicle is a differential value of a skid angle.
Since the derivative value of the side slip angle can be estimated and calculated from the vehicle body speed, the lateral acceleration of the vehicle, and the yaw rate, the degree of instability of the vehicle can be easily detected.

The invention according to claim 3 is characterized in that, in the invention according to claim 2, the correction amount by the correction means increases as the steering angular velocity increases.
Since the vehicle is likely to become unstable when the steering angular velocity is large, the traveling stability of the vehicle can be further improved by increasing the correction amount for the steering reaction force as the steering angular velocity increases.

According to the first aspect of the invention, even when the vehicle behavior is the same, the steering reaction force can be increased when the degree of instability of the vehicle is large. When the stability is improved and the degree of instability of the vehicle is small, the steering reaction force can be reduced, so that the vehicle deflection suppression performance can be reduced and the steering assist amount can be increased.
According to the invention which concerns on Claim 2, the instability degree of a vehicle can be detected easily.
According to the third aspect of the present invention, the traveling stability of the vehicle can be further improved by increasing the correction amount for the steering reaction force as the steering angular velocity increases.

Embodiments of a steering reaction force apparatus according to the present invention will be described below with reference to the drawings of FIGS. In the following embodiments, the present invention will be described in an aspect applied to an electric power steering device for a four-wheel vehicle.
First, the configuration of the electric power steering apparatus will be described with reference to FIG. The electric power steering apparatus includes a manual steering force generating mechanism 1, and the manual steering force generating mechanism 1 includes a steering shaft 4 integrally coupled to a steering wheel (operator) 3 and a connecting shaft 5 having a universal joint. Via a pinion 6 of a rack and pinion mechanism. The pinion 6 meshes with a rack 7a of a rack shaft 7 that can reciprocate in the vehicle width direction, and left and right front wheels 9, 9 as steered wheels are connected to both ends of the rack shaft 7 via tie rods 8, 8. ing. With this configuration, a normal rack and pinion type steering operation can be performed when the steering wheel 3 is steered, and the direction of the vehicle can be changed by turning the front wheels 9 and 9. The rack shaft 7 and the tie rods 8 and 8 constitute a steering mechanism.

  In addition, an electric motor 10 that supplies auxiliary steering force for reducing the steering force generated by the manual steering force generation mechanism 1 is disposed coaxially with the rack shaft 7. The auxiliary steering force supplied by the electric motor 10 is converted into thrust through a ball screw mechanism 12 provided substantially parallel to the rack shaft 7 and is applied to the rack shaft 7. For this purpose, a drive-side helical gear 11 is integrally provided on the rotor of the electric motor 10 through which the rack shaft 7 is inserted, and a driven-side helical gear 13 that meshes with the drive-side helical gear 11 is provided at one end of the screw shaft 12 a of the ball screw mechanism 12. The nut 14 of the ball screw mechanism 12 is fixed to the rack 7.

  The steering shaft 4 is provided with a steering angular velocity sensor 15 for detecting the steering angular velocity of the steering shaft 4, and a pinion is installed in a steering gear box (not shown) that houses the rack and pinion mechanism (6, 7a). A steering torque sensor 16 for detecting a steering torque acting on the steering wheel 6 is provided. The steering angular velocity sensor 15 outputs an electrical signal corresponding to the detected steering angular velocity, and the steering torque sensor 16 outputs an electrical signal corresponding to the detected steering torque to the steering control device 20, respectively.

  Further, at appropriate positions of the vehicle body, a lateral acceleration sensor 17 for detecting lateral acceleration applied in the vehicle width direction of the vehicle, a yaw rate sensor (vehicle behavior detecting means) 18 for detecting the yaw rate of the vehicle, and the vehicle body speed are set. A vehicle speed sensor 19 for detection is attached. The lateral acceleration sensor 17 is an electrical signal corresponding to the detected lateral acceleration, the yaw rate sensor 18 is an electrical signal corresponding to the detected yaw rate, and the body speed sensor 19 is an electrical signal corresponding to the detected body speed. 20 is output.

  The steering control device 20 determines a target current to be supplied to the electric motor 10 based on a control signal obtained by processing the input signals from these sensors 15 to 19, and supplies the electric current to the electric motor 10 via the drive circuit 21. Thus, the output torque of the electric motor 10 is controlled to control the auxiliary steering force in the steering operation.

Next, output torque control of the electric motor 10 in this embodiment will be described with reference to the control block diagram of FIG.
The steering control device 20 includes auxiliary steering torque determining means 31, auxiliary reaction force torque determining means (steering reaction force device) 32, target current determining means 33, and output current control means 34.
The auxiliary steering torque determining means 31 determines the auxiliary steering torque based on output signals from the steering angular velocity sensor 15, the steering torque sensor 16, and the vehicle body speed sensor 19. Since the method for determining the auxiliary steering torque in the auxiliary steering torque determining means 31 is the same as that of the known electric power steering, detailed description thereof will be omitted. In general, the auxiliary steering torque decreases as the steering angular velocity increases, and the steering torque becomes smaller. The auxiliary steering torque is set so as to increase as the vehicle speed increases, and the auxiliary steering torque decreases as the vehicle body speed increases.

The auxiliary reaction force torque determining means 32 determines the auxiliary reaction force torque TA based on the output signals of the steering angular velocity sensor 15, the lateral acceleration sensor 17, the yaw rate sensor 18, and the vehicle body speed sensor 19. The process for determining the auxiliary reaction force torque TA will be described in detail later.
The target current determination unit 33 calculates the target output torque of the electric motor 10 by subtracting the auxiliary reaction force torque determined by the auxiliary reaction force torque determination unit 32 from the auxiliary steering torque determined by the auxiliary steering torque determination unit 31. A target current corresponding to the target output torque is determined based on a known output characteristic of the electric motor 10.
The output current control unit 34 controls the output current to the motor 10 so that the actual current of the motor 10 matches the target current determined by the target current determination unit 33, and outputs it to the drive circuit 21.

Next, the process of determining the auxiliary reaction force torque TA by the auxiliary reaction force torque determining means 32 will be described in detail.
The auxiliary reaction force torque determining means 32 basically determines the steering reaction force according to the vehicle behavior (yaw rate in this embodiment) based on the vehicle body speed V, the steering angular velocity ω, and the vehicle yaw rate γ. The reaction force is corrected according to the degree of instability of the vehicle, and the amount of correction for the steering reaction force is increased as the degree of instability of the vehicle increases. In addition, since the possibility that the vehicle becomes unstable increases as the steering angular velocity ω increases, the correction amount for the steering reaction force increases as the steering angular velocity ω increases.

Then, the side slip angle differential value Δβ of the vehicle is employed as a parameter for the degree of vehicle instability. The side slip angle β of the vehicle refers to an angle formed by the traveling direction of the vehicle and the longitudinal axis of the vehicle, and the side slip angle β is obtained by time-differentiating the side slip angle β. Note that the side slip angle differential value Δβ is more suitable as the parameter of the degree of vehicle instability than the side slip angle β.
By the way, it is known that the lateral acceleration Gy of the vehicle can be estimated from the equation (1) based on the vehicle speed V, the yaw rate γ of the vehicle, and the side slip angle differential value Δβ of the vehicle from the physical relationship of the state quantity of the vehicle motion. (See, for example, JP-A-2003-146154).
Gy = V (γ + Δβ) (1)
Based on this, the side slip angle differential value Δβ can be calculated from the equation (2).
Δβ = (Gy / V) −γ Expression (2)
In this embodiment, the side slip angle differential value Δβ is estimated and calculated based on the output signals of the steering angular velocity sensor 15, the yaw rate sensor 18, and the vehicle body speed sensor 19. Thereby, the degree of instability of the vehicle can be easily detected.

Next, the auxiliary reaction force torque determination process executed in the auxiliary reaction force torque determination means 32 will be described with reference to the flowchart shown in FIG. 3 and the block diagram shown in FIG. The auxiliary reaction force torque determination process routine shown in the flowchart of FIG. 3 is repeatedly executed by the steering control device 20 at regular intervals.
First, in step S101, referring to the first auxiliary reaction torque table 41 shown in FIG. 4, the auxiliary reaction force torque (hereinafter referred to as the steering angular velocity ω) based on the output signals of the steering angular velocity sensor 15 and the vehicle body speed sensor 19 is described below. T1) (referred to as auxiliary reaction torque angular velocity component). The first auxiliary reaction torque table 41 is a table having the steering angular velocity ω set for each vehicle speed V as an address, and as the steering angular velocity ω increases, the auxiliary reaction force torque angular velocity component T1 increases, and the vehicle speed V increases. The auxiliary reaction torque angular velocity component T1 is set so as to increase as it increases.

Next, the process proceeds to step S102, with reference to the second auxiliary reaction force torque table 42 shown in FIG. T2) (referred to as auxiliary reaction force torque yaw rate component). The second auxiliary reaction torque table 42 is a table that uses the yaw rate γ set for each vehicle speed V as an address, and as the yaw rate γ increases, the auxiliary reaction force torque yaw rate component T2 increases and the vehicle speed V increases. The auxiliary reaction force torque yaw rate component T2 is set to be large.
That is, in this embodiment, the yaw rate γ is used as a vehicle behavior parameter, and the auxiliary reaction force torque (behavior reaction force) T2 increases as the yaw rate γ increases, in other words, as the vehicle behavior increases.

In step S103, Gy / V is calculated based on output signals from the lateral acceleration sensor 17 and the vehicle body speed sensor 19.
Next, proceeding to step S104, the differential value Δβ of the skid angle β is calculated {Δβ = (Gy / V) −γ}.

  Next, the process proceeds to step S105, and a correction coefficient K corresponding to the skid angle differential value Δβ obtained in step S104 is obtained with reference to the correction coefficient table 43 shown in FIG. The correction coefficient table 43 is a table having the side slip angle differential value Δβ set for each steering angular speed ω as an address. The correction coefficient K increases as the absolute value of the side slip angle differential value Δβ increases, and the steering angular speed ω increases. The correction coefficient K is set so as to increase. More specifically, the correction coefficient K becomes the minimum value when the side slip angle differential value Δβ is zero, and the correction coefficient increases as the absolute value of the side slip angle differential value Δβ increases until the absolute value of the side slip angle differential value Δβ reaches a predetermined value. K gradually increases, and after the absolute value of the side slip angle differential value Δβ reaches a predetermined value, the correction coefficient K is set constant. When the side slip angle differential value Δβ is the same, the correction coefficient K is set to a larger value as the steering angular velocity ω increases.

Next, the process proceeds to step S106, and the auxiliary reaction force torque angular velocity component T1 obtained in step S101, the auxiliary reaction force torque yaw rate component T2 obtained in step S102, and the correction coefficient K obtained in step S105 are used. TA is calculated by the following equation (3).
TA = (T1 + T2) K Formula (3)
When the auxiliary reaction torque TA is calculated in this way, even when the vehicle body speed V, the steering angular velocity ω, and the yaw rate γ are the same, when the side slip angle differential value Δβ is small, that is, when the degree of instability of the vehicle is small, Since the correction coefficient K is small, the auxiliary reaction force torque TA is set small, and when the side slip angle differential value Δβ is large, that is, when the degree of instability of the vehicle is large, the correction coefficient K is large, so the auxiliary reaction force torque TA is large. Is set. As a result, when the vehicle is stable, the vehicle deflection suppression performance can be reduced and the steering assist amount by the electric motor 10 can be increased, and when the vehicle is unstable, the vehicle deflection suppression performance can be increased and the running stability of the vehicle can be increased.
Further, since the correction coefficient K increases as the steering angular velocity ω increases, the auxiliary reaction force torque TA is set larger, and the running stability of the vehicle can be further improved.

  Next, the process proceeds to step S107, where it is determined whether or not the auxiliary reaction force torque TA calculated in step S106 is greater than the auxiliary reaction force torque maximum value Tmax, and the determination result in step S107 is “NO” (TA ≦ Tmax ), The process proceeds to step S108. If the determination result in step S107 is “YES” (TA> Tmax), the process proceeds to step S109, where the auxiliary reaction force torque maximum value Tmax is set to the auxiliary reaction force torque TA, The process proceeds to S108. That is, the process of step S109 functions as a limiter that prevents the auxiliary reaction force torque TA from exceeding the auxiliary reaction force torque maximum value Tmax.

In step S108, it is determined whether or not the auxiliary reaction force torque TA calculated in step S106 is smaller than the auxiliary reaction force torque minimum value −Tmax, and the determination result in step S108 is “NO” (TA ≧ −Tmax). If the determination result in step S108 is “YES” (TA <−Tmax), the process proceeds to step S110, where the auxiliary reaction force torque minimum value −Tmax is set to the auxiliary reaction force torque. The execution of this routine is once ended by setting TA. That is, the process of step S110 functions as a limiter that prevents the auxiliary reaction force torque TA from becoming smaller than the auxiliary reaction force torque minimum value −Tmax.
In this embodiment, the instability detection means is realized by the steering control device 20 executing the process of step S104, and the correction means is realized by executing the process of step S106.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, in this embodiment, the yaw rate of the vehicle is used as a parameter for vehicle behavior, but the lateral acceleration of the vehicle may be used as a parameter for vehicle behavior instead of or in addition to the yaw rate.
Further, the steering reaction force device according to the present invention is not limited to the application to the electric power steering device of the above-described embodiment, but can also be applied to a steering device (SBW) of a steer-by-wire system. In the SBW, the operation element and the steering mechanism are mechanically separated, and a reaction force motor (reaction device) that applies a reaction force to the operation element and a steering mechanism are provided to steer the steered wheels. A steering system including a steering motor that generates force.

1 is a configuration diagram of an electric power steering device that is an embodiment of a steering reaction force device according to the present invention. FIG. FIG. 3 is a block diagram of motor output torque control in the electric power steering device. It is a flowchart which shows the auxiliary reaction force torque determination process in the said motor output torque control. It is a block diagram of the auxiliary reaction force torque determination processing.

Explanation of symbols

32 Auxiliary reaction force torque determining means (steering reaction force device)
S104 Instability detection means S106 Correction means

Claims (3)

In the steering reaction force device that controls the steering reaction force according to the vehicle behavior,
Instability detecting means for detecting the degree of instability of the vehicle;
Correction means for correcting the steering reaction force according to the degree of vehicle instability detected by the instability detection means,
The steering reaction force device is characterized in that the correction means increases a correction amount for the steering reaction force so that the steering reaction force increases as the degree of instability of the vehicle increases.   The steering reaction force device according to claim 1, wherein the degree of instability of the vehicle is a differential value of a side slip angle.   The steering reaction force device according to claim 2, wherein the correction amount by the correction means increases as the steering angular velocity increases.

Images